public class Test1 {
    //leetcode 97 交错字符串
    public boolean isInterleave(String s1, String s2, String s3) {
        //dp[i][j]表示s1串[0,i]位置的子串和s2串[0,j]之间的子串交错是否能够和s3串[0,i+j]之间的子串匹配
        int m = s1.length(), n = s2.length();
        if (m + n != s3.length()) return false;
        boolean[][] dp = new boolean[m+1][n+1];
        s1 = " " + s1;
        s2 = " " + s2;
        s3 = " " + s3;
        dp[0][0] = true;
        for (int i = 1; i <= n; i++) {
            if (s2.charAt(i) == s3.charAt(i)) dp[0][i] = true;
            else break;
        }
        for (int i = 1; i <= m; i++) {
            if (s1.charAt(i) == s3.charAt(i)) dp[i][0] = true;
            else break;
        }
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                dp[i][j] = (s1.charAt(i) == s3.charAt(i + j) && dp[i - 1][j])
                        || (s2.charAt(j) == s3.charAt(i + j) && dp[i][j - 1]);
            }
        }
        return dp[m][n];
    }
}
